2.10 Predefined Names

The following identifier is predefined as an object-like macro:

Table 2–3 Predefined Identifier


Identifier	Description
`__STDC__`	`__STDC__ 1 -Xc` `__STDC__ 0 -Xa`, `-Xt` Not defined `-Xs`

The compiler issues a warning if __STDC__ is undefined (#undef __STDC__). __STDC__ is not defined in -Xs mode.

A current list of predefinitions is given in the cc(1) man page.